1. Technical Field
The present invention relates to camera and illumination matching for an inspection system.
2. Background Information
Over the past several decades, the semiconductor has exponentially grown in use and popularity. The semiconductor has in effect revolutionized society by introducing computers, electronic advances, and generally revolutionizing many previously difficult, expensive and/or time consuming mechanical processes into simplistic and quick electronic processes. This boom in semiconductors has been fueled by an insatiable desire by business and individuals for computers and electronics, and more particularly, faster, more advanced computers and electronics whether it be on an assembly line, on test equipment in a lab, on the personal computer at one's desk, or in the home electronics and toys.
The manufacturers of semiconductors have made vast improvements in end product quality, speed and performance as well as in manufacturing process quality, speed and performance. However, there continues to be demand for faster, more reliable and higher performing semiconductors.
Product developers who are building semiconductors and like microelectronics must be able to provide ample illumination for the machine vision process. One type of illumination involves strobing, and it is critical during strobing of the illuminator that the camera shutter is timed correctly—and often this timing alone is not accurate enough to match intensities. Users of inspection equipment continue to demand better defect data thereby requiring better camera and illumination matching.
It is known that cameras that are installed on inspection equipment are pre-set with vendor default settings for camera gain and offset. However, this often results in large variations between systems. In addition, light sources, whether halogen or strobe, can have large variations in light output (photons) for a given applied voltage.
As a result, inspection system users desire that all inspection systems give the same signal output for a given signal input. The output signal is measured as the average CCD array or other sensor array value and the input signal is generated from light reflected off a target or item to be inspected.
Overall, for a given signal input, which is determined from the voltage applied to the light source, a large variation in signal output can occur from the physics of the light source and camera gain and offset settings.